Playpens of foldable and non-foldable types are known in the art. Most non-foldable playpens are bulky and occupy relatively large storage spaces, and are therefore hardly appreciated and liked by city-dwellers. Foldable playpens generally occupy smaller storage spaces and are therefore preferred by the city-dwellers. A plurality of joints and couplers are employed to interconnect the adjoining ends of the frame sections which, in turn, confine looped frames for forming a playpen. Locking devices are employed to prevent folding of the adjoining frame sections. However, accidental actuation of the locking devices may occur, thereby resulting in folding of the frame sections relative to each other, which action may injure a child playing in the foldable playpen.
In co-pending U.S. patent application Ser. No. 09/264,662 by the applicant, there is disclosed a playpen that includes a looped lower frame, a looped upper frame, a plurality of couplers, and a plurality of vertical posts. The looped lower frame includes a plurality of interconnected lower frame sections having adjoining ends. The looped upper frame is disposed above the looped lower frame, and includes a plurality of upper frame sections having adjoining ends. The couplers interconnect the adjoining ends of the upper and lower frame sections. Each of the couplers includes a tubular portion which has two opposite open ends for insertion of a pair of the adjoining ends of the upper and lower frame sections, and a socket portion which projects from the tubular portion between the open ends and which has a socket hole. The vertical posts bridge the upper and lower frames and are connected to the couplers. Each of the vertical posts has two ends respectively supported by the socket portion a corresponding one of the couplers in the upper frame and the socket portion of a corresponding one of the couplers in the lower frame.
It is noted that the vertical posts of the playpen of the aforesaid co-pending patent application are made to be as long as possible so as to be suitable for use by taller children as well. However, the longer vertical posts will made it inconvenient to put and take a small child in the playpen.